1. Field
One or more embodiments described herein relate to a battery.
2. Description of the Related Art
Unlike a primary battery, a rechargeable battery can be repeatedly charged and discharged. Low-capacity rechargeable batteries are used in portable devices such as mobile phones, notebook computers, and camcorders. High-capacity rechargeable batteries are widely used as power sources for hybrid and electric vehicles.
When used as a power source for a vehicle, a plurality of battery cells are connected by one or more bus bars to form a rechargeable battery module. Such a module includes an electrode assembly for charging and discharging. The electrode assembly includes a separator between positive and negative electrodes. The negative electrode includes a negative electrode current collector and a negative active material layer, while the positive electrode includes a positive electrode current collector and a positive active material layer.
The negative electrode current collector is made of aluminum and the positive current collector is made of copper. A negative terminal electrically connected to the negative electrode is made of aluminum, while a positive terminal electrically connected to the positive electrode is made of copper.
Because the melting point of aluminum is different from copper, it is difficult to bond the different metals by welding. In attempt to solve this problem, the terminals or bus bars of the battery module may be bonded by friction welding. However, friction welding increases manufacturing costs and decreases productivity.